It has been previously described that the production of light olefin hydrocarbons from a hydrocarbon feedstock can be increased by a process comprising the steps of: feeding a hydrocarbon feedstock into a pyrolysis furnace to conduct a pyrolysis reaction; separating reaction products, which are generated from the pyrolysis reaction, into a stream containing hydrogen and C4 or lower hydrocarbons, and a stream containing C5+ hydrocarbons, through a compression and fractionation process; recovering hydrogen, and C2, C3 and C4 olefin and paraffin hydrocarbons, respectively from the stream containing hydrogen and C4 or lower hydrocarbons; separating pyrolysis gasolines and a C9+ hydrocarbon-containing fraction from the stream containing C5+ hydrocarbons, using hydrogenation and separation processes; feeding a mixture of the separated pyrolysis gasolines, a hydrocarbon feedstock, and hydrogen into at least one reaction area; converting the mixture in the presence of a catalyst in the reaction area into an aromatic hydrocarbon compound which is rich in benzene, toluene, and xylene through dealkylation/transalkylation reactions, and into a non-aromatic hydrocarbon compound which is rich in liquefied petroleum gas through a hydrocracking reaction; separating reaction products of the mixture converting step into an overhead stream, which contains hydrogen, methane, ethane, and liquefied petroleum gas, and a bottom stream, which contains aromatic hydrocarbon compounds, and a small amount of hydrogen and non-aromatic hydrocarbon compounds, using a gas-liquid separation process; circulating the overhead stream into the compression and fractionation process; and recovering the aromatic hydrocarbon compounds from the bottom stream; see e.g. US 20060287561 A1. In the process described in US 20060287561 A1, the C9+ hydrocarbon-containing fraction produced by pyrolysis is separated and purged. A major drawback of the process of US 20060287561 A1 is that the aromatics yield is relatively low.